Prevalence of Substance Abuse Disorders in Cancer Patients

ABSTRACT: Drug abuse presents a complex set of physical and psychosocial issues that complicate cancer treatment and pain/symptom management. Most oncologists are not be well versed in either the conceptual or practical issues related to addiction. As a result, they often struggle in their attempts to effectively treat patients who are or have been substance abusers, and they find it difficult to understand issues of addiction in patients with pain who have no history of substance abuse. In the first installment of a two-part series, the authors explore the epidemiology of substance abuse. An examination of the distinctions between abuse and dependence leads to definitions of these terms appropriate for the oncology setting. Guidelines for assessing aberrant drug-taking behavior are also offered. Part 2, which will appear in the next issue of oncology, will discuss the clinical management of cancer patients with a history of substance abuse.[ONCOLOGY 12(4): 517-521, 1998]

Drug usage is surprisingly common in this country, as indicated by
statistics showing that almost one-third of the US population has
used illicit drugs, and an estimated 6% to 15% have a substance-use
disorder of some type.[1-3] The prevalence of drug use in this
country and its association with life-threatening diseases, such as
AIDS, cirrhosis, and some types of cancer,[4] ensures that problems
related to abuse and addiction will be encountered in oncology settings.

Drug abuse (current or even a remote history) presents a complex set
of physical and psychosocial issues that complicate cancer treatment
and pain/symptom management. Oncologists are generally not well
versed in either the conceptual or practical issues related to
addiction; thus, they struggle in their attempts to treat these
patients effectively, and they find it difficult to understand issues
of addiction in patients with pain who have no history of substance
abuse. In this article, we will examine important conceptual and
clinical aspects of addiction that can lead to better care of these
challenging patients.

Defining the Goals of Care

Concerns central to planning overall treatment of pain and cancer
vary with the patients addiction status. It is important to
appreciate the extremely heterogeneity of patients with a history of
abuse or addiction. Patients who are actively abusing illicit drugs,
alcohol, or prescription drugs pose clinical problems distinct from
patients in drug-free recovery and those in methadone maintenance programs.

Although these distinctions are useful, they still oversimplify the
variations within these populations, which can be further complicated
by the issues of which drugs they use and at what frequency. In
addition, drug abuse varies over time; appropriate diagnosis of the
patient may be complicated by this fluctuation and by other changes
in comorbid physical and psychosocial factors that influence drug
use. Certain changes in drug-taking behavior are inherent to cancer
illness and treatment and are accompanied by the development of
related psychological and physical symptoms.

The range of clinical problems presented by patients with
substance-abuse histories is diverse. Clinicians must monitor and
control drug use in all patients, a precaution often neglected in
those who are not substance abusers. This becomes a substantial task
in the treatment of active abusers, in addition to the complexity of
treating cancer in such patients.

In some cases, compliance with treatments for cancer may be so poor
that the substance abuse actually shortens life expectancy by
preventing the effective administration of oncologic therapy.
Outcomes may also be altered by the use of drugs in a manner that
negatively interacts with therapy or predisposes patients to other
serious morbidity. Defining the goals of care can be very difficult
when patients poor compliance contradicts their stated desire
for cancer treatment.

The stress of cancer, in addition to the impact of unchecked
substance abuse, can weaken an already fragile social support
network. Such a network would ordinarily be crucial for coping with
the chronic stressors associated with cancer and its treatment.

One important source of support is the patients relationships
with members of the treatment team. Concerns about drug abuse may
undermine the doctor-patient relationship and lead clinicians to
doubt the veracity of the history, the report of symptoms, and
compliance with therapy. Clinicians are usually unwilling to confront
this issue. This avoidance reduces the opportunity for resolution and
further undermines the therapeutic alliance with the staff.

Patients with a history of substance abuse often come from
backgrounds characterized by exploitation and neglect. They are
frequently distrustful, may question the teams good will, and
sometimes harbor negative expectations that become self-fulfilling
prophesies. Wariness about the doctor-patient relationship can lead
to disruption of assessment, management, and follow-up, resulting in
the failure of therapies intended to improve quality of life. If
illicit drug use or manipulative behavior occurs, extraordinary
efforts by the treatment team may be required to avoid a vicious
cycle of undertreatment, drug abuse, and diminished trust.

Epidemiology

Few studies have evaluated the epidemiology of substance abuse in
patients with cancer and other progressive medical illnesses.
Although prevalent in the general population, substance abuse appears
to be fairly rare within the large tertiary-care population with
cancer. In 1990, only 3% of inpatient and outpatient consultations
performed by the Psychiatry Service at Memorial Sloan-Kettering
Cancer Center were requested for management of issues related to drug
abuse. This indicates that concerns about substance abuse on the part
of referring oncologists were lower than the prevalence of these
problems in society at large, in general medical populations, and in
emergency medical departments.[1-3,5,6]

This low prevalence was also reported in the Psychiatric
Collaborative Oncology Group study, which assessed psychiatric
diagnoses in ambulatory cancer patients from several tertiary-care
hospitals.[6] Based on structured clinical interviews, less than 5%
of a large sample of ambulatory cancer patients met the criteria for
a substance-use disorder outlined in the third edition of the Diagnostic
and Statistical Manual for Mental Disorders (DSM-III).[7]

For several reasons, the low prevalence of drug abuse in cancer
center populations may not be representative of the true prevalence
in the cancer population overall. First, there is no compelling
reason to think that age-corrected substance abuse rates would be
lower in people with cancer than rates in the normal population (ie,
having cancer does not somehow protect against substance abuse).
Also, the relatively low prevalence of substance abuse among cancer
patients treated in tertiary-care hospitals may reflect institutional
biases or a tendency for patient underreporting in these settings.

Furthermore, many drug abusers are poor and therefore may feel
alienated from the health-care system; consequently, they often do
not seek care in tertiary-care centers. Finally, even those who are
treated in these centers may not acknowledge drug abuse for fear of
stigmatization. In support of this assertion, a recent survey of
patients admitted to a palliative-care unit uncovered findings
indicative of alcohol abuse in approximately 20%.[8]

Thus, the epidemiology of substance abuse in cancer patients remains
largely unstudied and needs of clarification.